Conventional induction motors have been used in various mechanical devices such as pumps, blowers (fans), and compressors to suppress and reduce energy consumption. To further reduce the power consumption, the efficiency of induction motors themselves has been improved and control methods for mechanical devices have been developed.
For example, Patent Literature 1 discloses a technology in which control is performed in a maximum steady-state rotation-speed range such that the acceleration rotation in which the mechanical device is accelerated and rotated by the motor and the inertial rotation in which the motor is de-energized and the mechanical device is rotated by inertia are repeated alternately, thereby maintaining the rotation of the mechanical device within the maximum steady-state rotation-speed range, and during the inertial rotation in which the motor is de-energized and the mechanical device is rotated by inertia, the motor is de-energized and thus the power consumption is reduced.